Publications

2980 results

  • Regioscan Zoetwatermaatregelen : verkennen van het perspectief van kleinschalige zoetwatermaatregelen voor de regionale zoetwateropgave

    Authors: Delsman, J.R.; Boekel, E. van; Reinhard, S.; Winkel, T. te; Loon, A.H. van; Bartholomeus, R.P.; Mulder, M.; Massop, H.T.L.; Polman, N.; Schasfoort, F.E. (2018)

    De Regioscan Zoetwatermaatregelen helpt bij de ontwikkeling van een zoetwaterstrategie door het in beeld brengen van de bijdrage van lokale maatregelen afgezet tegen de regionale zoetwatertekorten. Het instrument bestaat uit een kennissysteem Zoetwatermaatregelen en een rekenmodule. Het kennissysteem is een database waarin generieke maatregelinformatie is opgeslagen. Deze is te koppelen aan scenario-informatie over hydrologie en landbouwbedrijven. De rekenmodule berekent de ruimtelijke variërende effecten van maatregelen op droogte- en zoutschade, kosten en baten, zoetwatergebruik en neveneffecten en cumuleert deze voor deel- of beheergebieden. Uit de toepassing op twee proefgebieden blijkt in z’n algemeenheid dat het instrument goed bruikbaar is om snel inzicht te krijgen in de potentie van de maatregelen. Eén van de aanbevelingen is het instrument verder te valideren. Voor concrete investeringsbeslissingen zijn meer detailberekeningen nodig.

  • Regioscan Zoetwatermaatregelen : beperken watervraag landbouw door kleinschalige maatregelen

    Authors: Delsman, J.R.; Schasfoort, F.E.; Jeuken, A.B.M. (2018)

    Omdat zoetwatertekorten steeds talrijker worden, zoeken waterbeheerders met landbouwers naar manieren om de vraag te verminderen. Onbekend is in hoeverre kleinschalige maatregelen kunnen bijdragen aan de regionale zoetwateropgave en tegen welke kosten. In de Regioscan Zoetwatermaatregelen worden van maatregelen de kosten en baten voor een landbouwbedrijf doorgerekend. Op basis van geselecteerde maatregelen (hetzij op basis van bedrijfseconomische baten-kostenverhouding, hetzij geselecteerd door de waterbeheerder) worden regionale effecten op de zoetwatervraag ingeschat. Het instrument ondersteunt hiermee de dialoog tussen waterbeheerder en boer. Vooralsnog lijken baten van kleinschalige zoetwatermaatregelen alleen in specifieke gebieden op te wegen tegen de kosten.

  • Evolucao do dano num quebra-mar de taludes em cenarios de alteracoes climaticas

    Authors: Lemos, R.; Fortes, C.J.; Mendonca, A.; Rosa-Santos, P.; Taveira-Pinto, F.; Almeida, E. de; Hofland, B. (2018)
    Published in: 14. Congresso da Agua : gestao dos recursos hidricos - novos desafios (7-9 de marco de 2018, Evora) (2018), page 1-16

    No âmbito do projeto HYDRALAB+ (H2020-INFRAIA-2014-2015), foi realizado no LNEC um conjunto de ensaios em modelo físico bidimensional (2D) de um perfil de um quebra-mar de talude em enrocamento, construído à escala geométrica 1:30, para diferentes condições de agitação arítima e níveis de maré correspondentes a cenários de alterações climáticas. Estas experiências tinham como objetivo analisar o dano, o espraiamento e o galgamento, nesses cenários. Em paralelo, na FEUP, e em colaboração com Deltares, foram realizados testes com a mesma configuração de quebra-mar, mas utilizando um modelo físico tridimensional (3D), construído à escala geométrica 1:35. Os resultados obtidos permitiram analisar a evolução do dano no manto resistente do quebra-mar (talude de barlamar, talude de sotamar e cabeça), assim como o galgamento, para condições com e sem sobrelevação do nível médio do mar, considerando ou não a reconstrução do talude do quebra-mar entre testes consecutivos da mesma série de testes. Foram também realizados testes com ondas multidirecionais. O presente trabalho incide sobre a análise da evolução do dano para as diferentes sequências de tempestade em cenários de alterações climáticas. O dano é avaliado com base no tradicional método de contagem de blocos removidos e ainda com base no parâmetro adimensional do dano, S recorrendo a técnicas estereofotogramétricas. É também feita uma avaliação do parâmetro E2D. Em termos gerais, concluiu-se que não havia diferenças significativas entre os testes com danos cumulativos e com a reconstrução do quebra-mar após cada teste. Observou-se, também, que o dano era mais elevado na proximidade da superfície livre e que aumentava com a altura de onda significativa. Os danos foram, em geral, menores nos testes com ondas multidirecionais.

  • 14. Congresso da Agua : gestao dos recursos hidricos - novos desafios (7-9 de marco de 2018, Evora)

    Originally published in 2018

  • Measuring damage in physical model tests of rubble mounds

    Authors: Hofland, B.; Rosa-Santos, P.; Taveira-Pinto, F.; Almeida, E. de; Lemos, R.; Mendonca, A.; Fortes, C.J. (2017)

    This paper studies novel ways to evaluate armour damage in physical models of coastal structures. High-resolution damage data for reference rubble mound breakwaters obtained under the HYDRALAB+ joint-research project are analysed and discussed. These tests are used to analyse the way to describe damage, the influence of the sequence of testing, and touches on the possible influence of sea level rise. Results of two test programmes were used. Firstly, 3D physical model tests carried out at the University of Porto, in cooperation with Deltares, were used. Here a wide breakwater trunk was used for statistical reasons. Additionally, 2D test results from LNEC were analysed. Tests for a sea level rise scenario resulted in less damage to the seaside slope. In addition, clear differences between “cumulative damage” and “rebuild” test series were noticed. However, significant scatter was also observed in the result of tests carried out under identical conditions. It was also concluded that the damage to the trunk was lower in the tests with short-crested waves. The design values for the damage depth E2D proposed by Hofland et al. (2011) were partly in line with the experimental results presented. Since the relation between S and the depth of damage E does not hold true for nonstandard cases, it seems better to use a parameter based on the local damage depth when testing such a structure. The reliability of a damage number for a test on the stability of a trunk can be improved by either increasing the relative size (width) of the test section or repeating the test.

  • Herstelmaatregel groot zeegras in de Nederlandse Waddenzee : haalbaarheid van de doelstellingen onder de Kaderrichtlijn Water

    Authors: Duren, L.A. van; Katwijk, M.M. van (2015)

    In de Nederlandse Waddenzee is groot zeegras (Zostera marina) bijna verdwenen en daarmee scoort de Waddenzee "slecht" voor deze ecologische parameter onder de Kaderrichtlijn Water (KRW). Volgens modelvoorspellingen is er voldoende geschikt habitat voor deze soort, maar zeer waarschijnlijk is een tekort aan zaadaanvoer een belangrijke factor waardoor zeegras in de Nederlandse Waddenzee zich niet spontaan kan herstellen. In 2011 is begonnen met een herstelproject op basis van zaad uit de Duitse Waddenzee. De doelstelling was om op drie locaties in Nederland een dusdanig grote hoeveelheid zeegras uit te zaaien dat hier robuuste zeegraspopulaties zouden ontstaan met voldoende kritische massa om natuurlijke fluctuaties op te vangen. Het project moest tevens leiden tot een advies m.b.t. de haalbaarheid van de huidige KRW-doelstellingen. Uitzaai heeft plaatsgevonden in 2011 en 2012 en de ontwikkeling van zeegras in opgevolgd tot 2015. In 2012 en 2013 is op alle drie de locaties zeegras opgekomen. De totale verspreiding van zeegras in 2013 bedroeg 300 ha, zij het met een gemiddeld zeer lage bedekkingsgraad (<1 %). In dat jaar is, in tegenstelling tot andere jaren, nauwelijks zaadzetting opgetreden. In 2014 is een zeer sterke teruggang opgetreden van de zeegrasbedekking op alle locaties. Recent is gebleken dat er, naast de reeds bekende ziekteverwekker Labyrinthula, nog een andere ziekteverwekker (Phytophthora) in de Waddenzee zit die mogelijk de reproductie en kiemkracht van zeegraszaad aantast. Dit was bij aanvang van het project niet bekend. Dit heeft er mogelijk toe geleid dat er veel minder kiemkrachtig zaad in Nederland is uitgezaaid dan oorspronkelijk berekend was. Ondanks het feit dat de doelstelling van het project (een robuuste populatie zeegras) niet is gehaald, wordt op dit moment geadviseerd om de KWR doelstellingen voor zeegras te handhaven. De nieuwste kansenkaart voor groot zeegras bevestigt dat er waarschijnlijk voldoende geschikt habitat in de Waddenzee is. Geadviseerd wordt om een onderzoekstraject in te zetten naar methoden om de kieming van ingevoerd zeegras te verbeteren en te zoeken naar voldoende grote geschikte bronnen van zeegraszaad. Het is niet zeker dat dit inderdaad haalbaar zal zijn, gezien het feit dat groot zeegras ook in buurlanden een beschermde status heeft. Mogelijk zal daar onvoldoende draagvlak zijn om grote hoeveelheden zaadmateriaal te leveren voor herstel van deze soort in Nederland. Onderzoek in het buitenland heeft aangewezen dat herstel van deze soort een zaak kan zijn van lange adem.

  • The relation between land use and subsidence in the Vietnamese Mekong delta

    Authors: Minderhoud, P.S.J.; Coumou, L.; Erban. L.E.; Middelkoop, H.; Stouthamer, E.; Addink, E.A. (2018)
    Published in: Science of the total environment, volume 634 (2018), page 715-726

    The Vietnamese Mekong delta is subsiding due to a combination of natural and human-induced causes. Over the past several decades, large-scale anthropogenic land-use changes have taken place as a result of increased agricultural production, population growth and urbanization in the delta. Land-use changes can alter the hydrological system or increase loading of the delta surface, amplifying natural subsidence processes or creating new anthropogenic subsidence. The relationships between land use histories and current rates of land subsidence have so far not been studied in the Mekong delta. We quantified InSAR-derived subsidence rates for the various land-use classes and past land-use changes using a new, optical remote sensing-based, 20-year time series of land use. Lowest mean subsidence rates were found for undeveloped land-use classes, like marshland and wetland forest (~6–7 mm yr−1), and highest rates for areas with mixed-crop agriculture and cities (~18–20 mm yr−1). We assessed the relationship strength between current land use, land-use history and subsidence by predicting subsidence rates during the measurement period solely based on land-use history. After initial training of all land-use sequences with InSAR-derived subsidence rates, the land-use-based approach predicted 65–92% of the spatially varying subsidence rates within the measurement error range of the InSAR observations (RMSE = 5.8 mm). As a result, the spatial patterns visible in the observed subsidence can largely be explained by land use. We discuss in detail the dominant land-use change pathways and their indirect, causal relationships with subsidence. Our spatially explicit evaluation of these pathways provides valuable insights for policymakers concerned with land-use planning in both subsiding and currently stable areas of the Mekong delta and similar systems.

  • A stochastic model for drought risk analysis in The Netherlands

    Authors: Diermanse, F.L.M.; Mens, M.J.P.; Macian-Sorribes, H.; Schasfoort, F.E. (2018)
    Published in: Hydrology and earth system sciences (2018), page 1-20

    Population growth and economic developments increase the demand for water resources. Furthermore, climate change is often projected to have negative impacts on the availability of these water resources. Measures to reduce the risk of water shortages can be costly and often require long-term planning strategies. In the decision making process, a thorough understanding of these drought-related risks for the various water users is of crucial importance. Historic time series of climatologic and hydrological variables, used as input for water allocation and drought impact models, are generally too short to provide such a detailed understanding. This makes the case for using lengthy synthetic time series. The challenge is to develop synthetic time series that are realistic and representative for the current and future climate conditions. We present a stochastic model for generating realistic times series of meteorological and hydrological variables that characterise drought events. The model is applied to a case study in the Netherlands, but is generic in set-up and can thus be applied elsewhere as well. It is demonstrated that the main features of the historic time series are well reproduced. The generated synthetic times series provide valuable insights into the frequency and severity of droughts and help improve the assessment of drought risks.

  • Coastal oceanography for life guards and beach lovers : development and application of a mobile phone app for swimmer safety

    Author: Rooijen, A. van (2017)
    Published in: State NRM and Coastal Conference 2017 (29 to 31 August 2017 at Curtin University, Bentley, Perth) : adapting in a changing world (2017), page 62-65

    The beach has always been a major attraction for people to spend their free time, and many beach goers enjoy spending time in the water. However, the ocean is a highly dynamic environment, and the local conditions (e.g. rip currents, waves) may vary greatly over relatively short periods of time. Therefore, swimmer safety is traditionally one of the major concerns for local governments and life guards. This paper describes the development of a mobile phone app that shows live predictions of ocean currents and beach width. The app is currently being used by the lifeguards at a Dutch beach, and is found to be a handy tool in enhancing swimmer safety. The generic setup and the global availability of numerical models and other data sources provide great opportunities to extend the application in functionality and to other regions in the world.

  • State NRM and Coastal Conference 2017 (29 to 31 August 2017 at Curtin University, Bentley, Perth) : adapting in a changing world

    Originally published in 2017

    The first Western Australian combined natural resource management and coastal conference. Themes: Under pressure - balancing needs ; Risk Management and Adaption Planning ; Responses - on-ground management ; Successful engagement ; Structural response - governance capacity and resilience ; Moving forward - managing capacity and addressing gaps.

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